The need for increased accuracy of target location determination is an important performance requirement for handheld targeting systems. Previously, the digital magnetic compass (DMC) was the primary component within systems used to determine the bearing (i.e., an angular measurement in the horizontal direction) between the observer and the target. The determined bearing was combined with a range to target, and inclination (i.e., an angular measurement in the vertical direction) of the target, and a location of the observer to provide a three-dimensional (3D) location of the target on the earth. However, any errors in the determined 3D location of the target may result in collateral damage (e.g., in a military context) when the target is located near one or more non-threat targets, for example in cases of urban engagement.
The horizontal bearing with respect to north of the target (“target azimuth”) is typically the largest contributor to an error in the determined 3D location of the target. DMCs are susceptible to large errors caused by variations in a local magnetic field, which may be caused by steel structures such as buildings or vehicles, nearby power lines, weapons, and even a tripod upon which a target location determination system is mounted. Azimuth errors of only 6 degrees result in target location errors of over 200 meters when the observer-to-target range is 2 kilometers.